1. Field of the Invention
The present invention relates to a signal transmission apparatus and a signal transmission method suitable for being applied to a case of transmitting image signals outputted from an image sensor having, for example, an RGB full pixel structure.
2. Description of the Related Art
A receiving system and an imaging system of an ultra-high definition image signal which surpasses an HD (High Definition) signal which is a current image signal (video signal) of 1920 sample×1080 lines per one frame has been hitherto developed. For example, a UHDTV (Ultra High Definition TV) standard which is a next-generation broadcasting format having four-times or sixteen-times the number of pixels of the current HD is standardized in international associations. As international associations, there exist ITU (International Telecommunication Union), SMPTE (Society of Motion Picture and Television Engineers) and so on.
Video standards proposed to ITU and SMPTE relate to image signals of 3840 samples×2160 lines and image signals of 7680 samples×4320 lines which are twice and four times the number of samples and the numbers of lines of the image signal of 1920 samples×1080 lines. The video standard which has been standardized in ITU is called LSDI (Large screen digital imagery), and the video standard which has been proposed to SMPTE is called UHDTV.
A sample structure of pixels in a 4096 horizontal sample, 3840 or 7680 horizontal sample standard prescribed in SMPTE2048-1 and SMPTE2036-0 (UHDTV) will be explained with reference to FIG. 15.
FIG. 15 is an explanatory view showing a system of R′, C′B′, Y′, Cb′Cr′, 4:4:4, as an example of the sample structure of the 4096 standards.
In the system, components of RGB or YCbCr are included in all samples.
As a frame used for explanation of FIG. 15, 4096 samples×2160 lines compose one frame. In the SMPTE standard, signals with dashes such as R′, G′ and B′ denote signals to which gamma correction and so on have been performed.
Heretofore, a broadcasting camera is used as a transmission apparatus transmitting image signals and a CCU (communication control unit) is used as a receiving apparatus receiving the image signals. A double-density Bayer arrangement is used in an imaging device of a currently-used camera which can output a 4 k×2 k signal (an ultra-high definition signal of 4 k samples×2 k lines). Here, in the double-density Bayer arrangement, pixels in a normal Bayer arrangement are arranged so as to be diagonal to one another at (angle of) 45 degrees. Each pixel has a half size of pixels in the normal Bayer structure in vertical and horizontal directions. Therefore, Gch has resolution corresponding to the number of pixels of 4 k×2 k.
A next-generation imaging device is assumed to have an RGB sample structure in the 4096 horizontal sample, 3840 or 7680 horizontal sample standard prescribed in three-plate SMPTE2048-1 or SMPTE2036-1 (UHDTV). However, it is considered that an image signal corresponding to 16-bit in raw data is transmitted from the camera to the CCU (communication control unit), not 10-bit, 12-bit quantization signals prescribed by SMPTE2048-1 or 2036-1 (UHDTV).
In JP-A-2005-328494 (Patent Document 1), a technique of transmitting 3840×2160/30 P, 30/1.001 P/4:4:4/12-bit signals as a kind of the 4 k×2 k signals at a bit rate of 10 Gbps or more is disclosed. A notation of [3840×2160/30 P] represents [the number of pixels in the horizontal direction]×[the number of lines in the vertical direction]/[the number of frames per one second]. A notation of [4:4:4] represents the ratio of [red signal R:green signal G:blue signal B] in the case of a primary-color signal transmission system and represents the ratio of [luminance signal Y:first color-difference signal Cb:second color-difference signal Cr] in the case of a color-difference signal transmission system.